Influence of free carriers on exciton ground states in quantum wells

The influence of free carriers on the ground state of the exciton at zero magnetic field in a quasi-two-dimensional quantum well doped with electrons is considered in the framework of the random phase approximation. The effects of the exciton-charge-density interaction and the inelastic scattering processes due to the Hartree-Fock electron-electron exchange interaction are taken into account. The effect of phase-space filling is considered using an approximate approach. The results of the calculation are compared with the experimental data available.Comment: 8 pages, 5 fugure

Luminescence spectra and kinetics of disordered solid solutions

We have studied both theoretically and experimentally the luminescence spectra and kinetics of crystalline, disordered solid solutions after pulsed excitation. First, we present the model calculations of the steady-state luminescence band shape caused by recombination of excitons localized in the wells of random potential induced by disorder. Classification of optically active tail states of the main exciton band into two groups is proposed. The majority of the states responsible for the optical absorption corresponds to the group of extended states belonging to the percolation cluster, whereas only a relatively small group of “radiative” states forms the steady-state luminescence band. The continuum percolation theory is applied to distinguish the “radiative” localized states, which are isolated in space and have no ways for nonradiative transitions along the tail states. It is found that the analysis of the exciton-phonon interaction gives the information about the character of the localization of excitons. We have shown that the model used describes quite well the experimental cw spectra of CdS(1−c)Sec and ZnSe(1−c)Tec solid solutions. Further, the experimental results are presented for the temporal evolution of the luminescence band. It is shown that the changes of band shape with time come from the interplay of population dynamics of extended states and spatially isolated “radiative” states. Finally, the measurements of the decay of the spectrally integrated luminescence intensity at long delay times are presented. It is shown that the observed temporal behavior can be described in terms of relaxation of separated pairs followed by subsequent exciton formation and radiative recombination. Electron tunneling processes are supposed to be responsible for the luminescence in the long-time limit at excitation below the exciton mobility edge. At excitation by photons with higher energies the diffusion of electrons can account for the observed behavior of the luminescence

Hybrid nanoparticles based on sulfides, oxides, and carbides

The methods for synthesis of hybrid nanoparticles based on sulfides, oxides, and carbides of heavy and transition metals were considered. The problem of the influence of the method of synthesis of the hybrid nanoparticles on their atomic structure, morphology of the nanomaterials, and functional properties was analyzed. The areas of practical use of the hybrid nanoparticles were proposed. © 2013 Springer Science+Business Media New York

Public policy instruments in (re)building national innovation capabilities: cases of nanotechnology development in China, Russia and Brazil

Atlanta Conference on Science and Innovation Policy 2011The paper seeks to understand the role of emerging technologies in breaking institutionally the development lock-in and supporting self-sustained growth through analyzing broad socioeconomic impacts of nanotechnology in the US, Russia, China and Brazil. The study provides comparative case study analysis and benchmarks the nations policies and development trajectories

ВЛИЯНИЕ ТЕХНОЛОГИИ ИЗГОТОВЛЕНИЯ КАТОДОВ НА КАЧЕСТВО ПОКРЫТИЙ ЛОПАТОК ТУРБИНЫ

Conducting comparative studies of the quality of pipe cathodes made by casting and granule metallurgy (GM), and assessing the quality of coating applied to blades by ion-plasma deposition with their application. Проведение сравнительных исследований качества трубных катодов, изготовленных методом литья и металлургией гранул (МГ), а также выполнить оценку качества покрытий, нанесенных на лопатки турбины методом ионно-плазменного осаждения c их применением.